Internal measuring gauge with a ring



y 4, 1954 M. c. SHAW ETAL 2,677,190

' INTERNAL MEASURING GAUGE WITH A RING Filed Jan. 10, 1952 INVENTORS Mi/fan G. Show Charles 0. Strung, Jr:

BYQWL W ATTORNEY Patented May 4, 1954 INTERNAL MEASURING GAUGE WITH A RING Milton 0. Shaw, Lexington, Mass, and Charles D.

Strang, Jr., Fond du Lac, Wis.

Original application August 24, 1945, Serial No. 612,520. Divided and this application January 10, 1952, Serial No. 265,913

(Granted under Title 35, U. S. Code (1952),

see. 266) 3 Claims.

This invention relates to measuring gages. This is a divisional application of our pending application Serial No. 612,520 which was filed on August 24, 1945, and is now abandoned.

An obj ect of this invention is to provide a ring dynamometer with mechanically operative means of stressing it in such direction as to expand the ring; and electrical means of detecting and measurin the strain of the ring so that the amount of enlargement of the ring may be used to determine the inside dimension of a cylinder or other worlr piece which is provided with a circular opening.

Ancillary objects will become apparent in followin the description of the illustrated form of the invention.

In the drawings:

Fig. 1 is a longitudinal sectional view of the device, portions being shown in elevation;

Fig. 2 is a transverse sectional View taken on the plane of line 22 of Fig. l and in the direction of the arrows;

Fig. 3 is a wiring diagram of the lamp indicating circuit of the device of Fig. 1 as applied while measuring a cylinder bore, and;

Fig. 4 is a wiring diagram of the strain gage indicating circuit.

It is to be understood that the term ring is used herein in a broad sense to comprehend a closed, continuous, curved beam of any configuration or cross-section. In the illustrated embodiment, a ring of circular configuration is used, since it represents the most simple and most easily fabricated of all dynamometer ring structures. Also, the term wire as used herein, comprehends a ribbon, sheet, bar or any other form or configuration of strain-sensitive means.

One of the diinculties commonly met in the use of strain measuring elements is the effect of a temperature differential between the respective arms of the electrical bridg circuit. This results in a change of resistance with an accompanying change of force or displacement of the measuring system-a condition referred to as zero drift. In order that zero drift be completely eliminated, it is essential that the pairs of strain measurin elements or gages 12, 43 and 44, 45 be kept at the same temperature. This is conveniently accomplished by placing adjacent bridge elements on adjacent surfaces of the dynamometer rings as shown in Fig. 1. Furthermore, the use of a closed ring of symmetrical design provides equal parallel paths from equally spaced points, thus tending to keep all strain gases at the same temperature level. Numerous dynamometer rings constructed in the manner of the foregoing description have proved to be completely free of zero drift when operated under a wide range of temperature conditions, even though the gages employed were constructed of wire having a high change in resistance With temperature.

By employing four active strain measurin elements as the respective arms in the electrical bridge circuit as shown in Fi 4, maximum change of resistance and therefore maximum strain measuring sensitivity is obtained. In addition to the foregoing advantages embracing temperature compensation and maximum strain measurin sensitivity, a closed continuous curved beam is convenient, compact and easily applied to the measurement of forces and linear displacement. By proper choice of material and range of operation, the output of the bridge circuit may be made to vary linearly with the applied force or linear displacement.

A dynamometer ring l! of elastic material, preferably metal, is provided with pairs of strainsensitive wire gages 12, 43 and 44, 45, the gages 43 and 45 being on the inner surface of the rin s1 while the gages 42 and 45 are on the outer surface thereof. Each gage is held in place by a standard means, as cement, and the gages constitute arms of a Wheatstone bridge circuit as disclosed in Fig. 4 and also in our copending application, Serial No. 612,520.

A ring expanding toggle assembly 66 is employed to deform the ring 4| until contact points il, :38 and 49 touch th internal surface to be measured. The previously calibrated change in resistance of the strain gages on the dynamometer ring is a measure of the diameter of the bore.

In detail, the toggle 46 consists of there pairs of arms 50 and 5!, 52 and 53, and 54 and 55. One end of each of said pairs is pin connected at 56 to the radially disposed bolts 5?, 53 and 59, respectively, passing through openings in the ring 41 The ends of these bolts are slotted to receive the outer ends of the toggle arms in pin connection therewith, and nuts 60, 6| and 62 lock the bolts to the ring 4!. The inner ends of arms 50, 52, and 54 are pin connected at 63 to a collar 64 provided with suitable lugs 65 for the reception thereof. The collar 64 is rigidly fixed, as by welding 66, to a hollow shaft 6! coaxially positioned therewith, and a sleeve 58 is coaxially positioned around shaft 61 and is engaged therewith by threads 69. The lower end of the sleeve 68 is differentially threaded as at 10, relative to threads 69, and receives a collar H in threaded engagement therewith. Toggle arms 5|, 53 and 55 are pin connected at 72 to the collar H which is provided with lugs 13 for the reception of these arms. The top ends of shaft 61 and sleeve 68 are enlarged and knurled to provide a finger grip, and on the top of the shaft 61 there are mounted electric lamps 19, 80 and 8|.

The bolts 5'5, 58 and 59 are axially bored and threaded to receive non-conducting fixtures 13, I4 and 15, to the end of which are fastened contacts 49, 48 and 41, respectively. Conductors 16, 18 and '17 electrically connect lamps 8!, 19 and 80 to contacts 49, 41 and 48, respectively, and the conductors are passed through the hollow shaft 67 and a lateral outlet aperture 82 in the lower end of the shaft 61.

In operation, the internal measuring device is calibrated against standard gage blocks. The measuring device, as a unit, is inserted into a cylinder bore or other hole 83 to be measured, and expanded by means of the differential screw toggle 49 until contact of the points 49, 48 and 41 with the inner periphery of the bore 83 is indicated by the lamps 8|, 8!! and 19. As the ring 4| is thus stressed and hence deformed, the amount of strain or deformation is transmitted to the wire gages 42, 43 and 44, 45. But since these gages are arms of the Wheatstone bridge in the balanced circuit (Fig. 4), a direct reading may be taken from the potential responsive indicating device 35, which may be calibrated to indicate diameter, circumference and radius of the bore, or one or a pair of these dimensions.

Since numerous modifications may be made without departing from the inventive concept, limitation is sought only in accordance with the scope of the following claims.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

We claim:

1. In an inside dimension measuring device, the combination of an elastic closed ring provided with strain-sensitive gages on the inner and outer surfaces thereof, a balanced circuit having a 4 bridge of which said gages constitute arms, means for stressing said ring in such direction as to increase the diameter thereof to thereby strain said ring whereby said gages detect the amount of said strain, said means including a pair of coaxial elements axially movably connected together, arms pivoted at their outer end to said ring, means connecting the inner ends of certain of said arms to one of said coaxial elements, means connecting the inner ends of the remaining arms to the other of said coaxial elements, contacts carried by said closed ring and projecting outwardly of the outer surface thereof so that the contacts are adapted to touch the work piece retaining said ring spaced from the Work piece, insulating means between said contacts and said ring, and electrically operative indicators connected with said contacts to inform of the touching of a work piece by the contacts.

2. The combination of claim 1 and; said indicators being disposed on one of said coaxial elements and movable therewith.

3. The combination of claim 2, and; said one of said elements having a passage extending axially therethrough, electrical conductors extending through said passage and connected to said contacts and to said indicators.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,436,355 Parker Nov. 21, 1922 1,958,864 Richardson May 15, 1934 2,316,975 Ruge Apr. 20, 1943 2,445,068 Jackson July 13, 1948 2,566,970 Swensson Sept. 4, 1951 2,569,949 Prescott Oct. 2, 1951 FOREIGN PATENTS Number Country Date 4,190 Austria May 25, 1901 OTHER REFERENCES Theis, publication Aircraft Engineering, April 1943, pages 106-109, of record in parent application, S. N. 612,520. 

